This region covers parts of southeastern California, southwestern Arizona, and northern Mexico, including Baja California and Sonora. The landscape is a classic example of a basin and range province. This means the area is filled with long mountain ranges separated by wide, flat valleys. The terrain includes rocky mountains, sandy plains, and large fans of soil and rock at the base of hills. Elevations start at sea level and climb to over 4,593ft (1,400 m). The ground is made of many different types of ancient rocks, such as volcanic and metamorphic stones. The soil is mostly very dry and sandy.

The climate is a dry subtropical desert. Summers are extremely hot, with temperatures often climbing above 110F (43C). Winters are mild, but you can still expect chilly nights where temperatures drop near 32F (0C). Rainfall is unique because it happens in two different seasons. Winter rains usually move in from the west, while summer rains come from the east. Most of the region gets about 8.1in (206 mm) of rain a year, though some spots only get 3in (75 mm) while others get up to 22in (560 mm). The driest parts may see as little as 3.9in (100 mm) of rain.

Plants in this region have special ways to survive the heat and drought. You will find many types of cacti, such as the giant saguaro and the prickly pear. Other common plants include the palo verde tree, creosote bush, and ocotillo. In the middle of the region, the plants are typical desert scrub. However, as you move toward the southern parts, the environment becomes more tropical. There, you can find deciduous thorn forests where trees lose their leaves to save water.

Water is a precious resource in this desert. Most streams are ephemeral, which means they only flow after a heavy rain. The Colorado River is the largest and most important water source, even though its source is far away in the mountains. In the south, rivers like the Yaqui and Mayo flow down from the mountains to provide water. Because water is so important, people use a lot of it for farming. Sometimes, using too much groundwater or having salt in the soil can make it difficult to grow crops in certain areas.

A wide variety of animals live here. You might see desert bighorn sheep on the cliffs or javelinas in the brush. Other animals include the coyote, bobcat, and desert tortoise. Small creatures like the kit fox and kangaroo rat are also common. Birds like the elf owl and red tailed hawk are frequently seen in the sky. The region is also closely linked to the marine life found in the nearby Sea of Cortez.

A fun fact about this area is that the giant saguaro cactus can live for more than 150 years. These massive plants grow very slowly and might not even grow their first arm until they are 75 years old!

DesertsRWild

Planting Areas

My Backyard

Wildlife Features

About the Sonoran Basin and Range ecoregion

About the City of Marana-Santa Cruz River watershed